DESCRIPTION: (Adapted from the investigator's Specific Aims) In this renewal application, Dr. Soares proposes to introduce some minor modifications in his protocol to construct libraries enriched for full-length cDNAs. Second, he will construct normalized libraries enriched for full-length cDNAs from size fractionated mRNAs representing a variety of human fetal and adult tissues. And third, cDNAs will be directionally cloned into an expression vector (pcDNA3.1/Zeo) which allows for high-level, stable or transient expression in a variety of mouse embryonic and adult tissues.